very low encoding frame rate using WMAsfWriter filter

tfs

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Oct 30, 2009, 11:20:03 AM10/30/09

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I build a DirectShow (Windows SDK 6.1) + WMF11 encoder graph, and create a
WMAsfWriter filter for creating ASF files. Below is the simplest form of my
encoder graph (stripped out all video preview and transformation filters):

Crossbar --> video capture filter --> WMAsfWriter
audio capture filter --> WMAsfWriter (the same one above)

IWMProfile is created from loading a custom .prx file with the following
stream settings:

PAL 25 fps, 720x576, key frame interval = 1 sec, smoothness = 100%
video: CBR, codec = Windows Media Video 9 Advanced, 4 Mbps
audio: CBR, codec = Windows Media Audio 9.2, 64kbps 44 kHz
stream: none

The only thing I set into the WMAsfWriter filter is the output filename and
use the above IWMProfile to configure the filter.

After creating a video files of few minutes long, and play it back in WMP11,
I discover that the video frame rate is much lower than 25 fps: 20 fps is the
best I've had, and typically it is only about 12 fps.

Now, if I use Windows Media Encoder app directly, and use exactly the same
A/V capture devices and .prx profile, recording for exactly the same
duration, it can achieve 24.x fps.

What is wrong with WMAsfWriter? Is there anything I can tune this thing up?
I had observed the CPU load when encoding using this filter, and it didn't
hit 100% (but high enough already). As described above, there even is't any
video preview added at all (can't imagine if I add it ...).

Or is it just a bad choice using WMAsfWriter to encode video from the
capture hardware?

thomas r.

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Oct 31, 2009, 11:03:00 AM10/31/09

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> After creating a video files of few minutes long, and play it back in WMP11,
> I discover that the video frame rate is much lower than 25 fps: 20 fps is the
> best I've had, and typically it is only about 12 fps.

Can this be a problem of the capture source?
My USB cameras switch down from 30 to ~10 fps in the dark.

tfs

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Nov 2, 2009, 8:14:01 AM11/2/09

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"thomas r." wrote:

> .
>

No. I am using the Winnov Videum Duo capture card, and the video source
comes from a PAL DVD player, so there is a very steady video input signal.

Also, after calling IConfigAsfWriter2::ConfigureFilterUsingProfile(), do I
still need to obtain the video input-pin and check/set the frame-rate? My
thought is I don't think so, thatg is what
IConfigAsfWriter2::ConfigureFilterUsingProfile() should have done.

Also, it seems like I am the only one who experiences this problem; I didn't
find any poster in here experiencing the same problem as mine when using the
WMAsfWriter filter. ??????

thomas r.

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Nov 5, 2009, 6:10:21 PM11/5/09

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> No. I am using the Winnov Videum Duo capture card, and the video source
> comes from a PAL DVD player, so there is a very steady video input signal.

So it can't be - the asf writer should react in the same way to your
capture card as it does to my USB cameras. And I get 30 fps (with cams
looking at daylight) in 640*480 with an old Pentium 4 2.8 GHz.
Did you try it on a faster PC? Did you try writing uncompressed Video?
A varying framerate still sounds like a problem with the cpu power. If
there was a constant low rate I'd bet it is a problem with the
settings of the capture card's filter output pin.

Thomas